[Mesa-dev] [PATCH] nir: Copy-propagate vecN operations that are actually moves

[Kenneth Graunke]

On Thursday, February 19, 2015 10:03:15 PM Jason Ekstrand wrote:
> We were already do this for ALU operations but we haven't for non-ALU
> operations.  This changes that.
> 
> total NIR instructions in shared programs: 2039883 -> 2022338 (-0.86%)
> NIR instructions in affected programs:     1768850 -> 1751305 (-0.99%)
> helped:                                    14244
> HURT:                                      124

It's great to see these cleaned up - programs were littered with

ssa_1 = vec4(ssa_2.x, ssa_2.y, ssa_2.z, ssa_3.w);

Now they're much better.

> total FS instructions in shared programs: 4083960 -> 4084036 (0.00%)
> FS instructions in affected programs:     7302 -> 7378 (1.04%)
> helped:                                   12
> HURT:                                     51

This is strange.  At least many programs aren't affected.
Presumably, the backend was cleaning up most of these MOVs anyway, and
tidying up the NIR code will help down the road.

> Signed-off-by: Jason Ekstrand <jason.ekstrand at intel.com>

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

> ---
>  src/glsl/nir/nir_opt_copy_propagate.c | 45 ++++++++++++++++++++++-------------
>  1 file changed, 29 insertions(+), 16 deletions(-)
> 
> diff --git a/src/glsl/nir/nir_opt_copy_propagate.c b/src/glsl/nir/nir_opt_copy_propagate.c
> index dd0ec01..ee78e5a 100644
> --- a/src/glsl/nir/nir_opt_copy_propagate.c
> +++ b/src/glsl/nir/nir_opt_copy_propagate.c
> @@ -53,22 +53,6 @@ static bool is_move(nir_alu_instr *instr)
>  
>  }
>  
> -static bool
> -is_swizzleless_move(nir_alu_instr *instr)
> -{
> -   if (!is_move(instr))
> -      return false;
> -
> -   for (unsigned i = 0; i < 4; i++) {
> -      if (!((instr->dest.write_mask >> i) & 1))
> -         break;
> -      if (instr->src[0].swizzle[i] != i)
> -         return false;
> -   }
> -
> -   return true;
> -}
> -
>  static bool is_vec(nir_alu_instr *instr)
>  {
>     for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++)
> @@ -80,6 +64,35 @@ static bool is_vec(nir_alu_instr *instr)
>            instr->op == nir_op_vec4;
>  }
>  
> +static bool
> +is_swizzleless_move(nir_alu_instr *instr)
> +{
> +   if (is_move(instr)) {
> +      for (unsigned i = 0; i < 4; i++) {
> +         if (!((instr->dest.write_mask >> i) & 1))
> +            break;
> +         if (instr->src[0].swizzle[i] != i)
> +            return false;
> +      }
> +      return true;
> +   } else if (is_vec(instr)) {
> +      nir_ssa_def *def = NULL;
> +      for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
> +         if (instr->src[i].swizzle[0] != i)
> +            return false;
> +
> +         if (def == NULL) {
> +            def = instr->src[i].src.ssa;
> +         } else if (instr->src[i].src.ssa != def) {
> +            return false;
> +         }
> +      }
> +      return true;
> +   } else {
> +      return false;
> +   }
> +}
> +
>  typedef struct {
>     nir_ssa_def *def;
>     bool found;
> 
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